It is conventional practice to form a wiring line in a fine wiring groove, a hole, or a resist opening provided in the surface of a semiconductor wafer etc., or to form a bump (protruding electrode), which is electrically connected with an electrode on a packaging substrate etc., on the surface of a semiconductor wafer etc. Known methods for forming such wiring lines and bumps include, for example, an electroplating method, a vapor deposition method, a printing method, and a ball bump method, etc. Due to increase in the number of I/Os and the reduction in pitch of semiconductor chips in the recent years, the electroplating method which allows for miniaturisation and relatively stable performance has been widely used.
In the process of forming a wiring line in a resist opening by an electroplating method, the wiring line is formed in the resist opening, and thereafter, resist formed on the substrate is removed, and a seed layer (or a barrier metal) is etched. The process of forming the wiring line, the process of removing the resist, the etching process of the seed layer and the like are performed by dipping the substrate into a processing bath accommodating a predetermined processing solution. As the processing bath, a processing bath which is capable of accommodating a substrate upright (vertically) is known (Re-publication of PCT International Publication No. WO 01/68952, for example).
In the case where processing is performed with a substrate vertically accommodated, when a substrate holder holding the substrate is transferred, the substrate holder is transferred above the processing bath with the substrate holder being also oriented in the upright (vertical) direction. If another substrate holder is put in and taken out from the processing bath when the substrate holder is transferred with the substrate holder being oriented in the upright direction like this, the other substrate holder becomes an obstacle of transfer of the substrate holder. Therefore, while another substrate holder is put in and taken out from the processing bath, transfer of the substrate holder needs to be awaited, and there arises the problem of reduction in the throughput of the entire substrate processing apparatus.